The present invention relates to a jet flow generating apparatus that generates a jet flow and cools a heat generating member such as an electronic part with the generated jet flow, an electronic device that is equipped with the jet flow generating apparatus, and a jet flow generating method.
As the performance of PCs (Personal Computers) has been advanced, the calorific powers of heat generating members such as ICs (Integrated Circuits) have been adversely increased. To solve such a problem, various heat radiating technologies have been proposed and/or practically used. As one of heat radiating methods, there is a method wherein heat radiating fins made of metal such as aluminum are attached to an IC, and the generated heat by the IC is transferred to the fins to radiate the heat. Alternatively, there is another method wherein hot air that stays in a casing of a PC may be forcedly exhausted with a fan, and cool air around the PC is forcedly introduced around the heat generating members with the fan. Alternatively, there is still another method wherein, with both heat radiation fins and a fan, while the contact area of the heat generation member with air is increased with the heat radiation fins, the fan forcedly exhausts the hot air around the heat radiation fins.
However, there is a problem that a thermal boundary layer of fin surface is generated on the downstream side of the heat radiation fins by the forced conversion of air by the fan, it is difficult to effectively take away the heat. To solve such a problem, for example, it is considered that the air speed of the fan may be increased so as to thin the thermal boundary layer. But, there is a problem that nose of a bearing portion of the fan and wind cut noise of the fan are generated by increasing the number of rotations of the fan in order to increase the air speed.
As a method for breaking the thermal boundary layer and effectively releasing the heat of the heat radiation fins, a combined jet flow can be used. In this method, air that is moved by a piston or the like is jetted from a hole formed on one end of a chamber. The air jetted from this hole is called a combined jet flow. The combined jet flow promotes the mixing of air, breaks the thermal boundary layer, and more effectively radiates the heat than the forced convection generated by a conventional fan. See U.S. Pat. No. 6,123,145.
However, according to the technology described therein, since air vibration generated by a reciprocating motion of the piston is propagated as a sound wave, the sound is heard as noise. Further, as the clock frequencies of ICs have been increased in recent years, the heats generated by the ICs have been proportionally increased. Thus, to break the thermal boundary layer formed in the vicinity of the heat radiation fins, much more air should be discharged to the IC and the heat radiation fins than before. Thus, in the apparatus shown in FIG. 1A and so forth of U.S. Pat. No. 6,123,145 that vibrates the vibration film and jets air, it is necessary to increase the amplitude of the vibration so as to increase the jet flow amount of the air. Thus, if the frequency of the vibration film is in an audio frequency range, the noise of the vibration film will become a problem to solve.